Identification of Preoperative Fat-Free Mass Index for the Prognosis of Curatively Resected Esophageal Cancer

Background The progressive, systemic depletion of muscle mass is a poor prognostic factor for various types of cancers. However, the assessment of body composition for patients with esophagectomy remains unclear. Therefore, we evaluated the significance of the fat-free mass index (FFMI) and estimated the appropriate cutoff value. Methods We compiled clinicopathological characteristics of patients who underwent curative operation for esophageal cancer between October 2013 and March 2018 at Toranomon Hospital and reviewed them until December 2020. We analyzed the short- and long-term outcomes, compared to conventional nutritional factors, and calculated the area under the receiver operating characteristic (ROC) curve. Results A total of 200 patients were eligible for inclusion. FFMI was ineffective in predicting postoperative complications, with no correlation with other nutritional biomarkers. Preoperative low FFMI led to poor overall survival (OS), and the lower cutoff values based on the time-dependent ROC analysis were 14.4 and 16.8 kg/m 2 in women and men, respectively. Multivariate analysis for OS revealed that low FFMI ( p = 0.010, HR 2.437, 95% CI 1.234–4.815) and clinical stage ( p = 0.010, HR 4.781, 95% CI 1.447–15.796) were independent prognostic factors. The 3-year survival rates were 68.9% in low FFMI and 88.6% in normal FFMI. Conclusions The low FFMI was not predictive of postoperative complications but an independent prognostic factor in esophageal cancer with curative resection, having no correlation with other biomarkers. Our cutoff FFMI values could be useful in selecting the target for muscle improvement programs.